Plus, one of the ultra secretive billionaire Koch brothers breaks his silence about the 2016 race in a revealing ABC News exclusively.

JONATHAN KARL, ABC NEWS CORRESPONDENT: So is it possible another Clinton could be better than another Republican this time around?

CHARLES KOCH, KOCH INDUSTRIES: It's possible.

It's possible.

ANNOUNCER: And Bernie's long shot campaign.

SEN. BERNIE SANDERS (I-VT), DEMOCRATIC PRESIDENTIAL CANDIDATE: I am in this race to the end.

ANNOUNCER: He's pushing harder than ever despite a nearly impossible path to the nomination. With tough contests ahead, will he damage Hillary Clinton before he's done?

Bernie Sanders speaks out live.

From ABC News, it's THIS WEEK.

Here now, chief anchor, George Stephanopoulos.

GEORGE STEPHANOPOULOS, ABC HOST: Good morning.

Donald Trump is riding high after his crushing win this week in New York, poised to pull away with a possible sweep in Tuesday's primaries. And now his team is reaching out to the GOP with the promise of a more presidential Trump,

TOM LLAMAS, ABC NEWS CORRESPONDENT (voice-over): For all of that talk, Donald Trump would tone it down...

TRUMP: I sort of don't like toning it down...

LLAMAS: -- the candidate has turned it up.

On Ted Cruz, just last week, he called him "Senator." Now this.

TRUMP: He's got zero personality because he lies like a thief, OK?

LLAMAS: A step back. Remember, this was to be the week Donald Trump would make a presidential pivot, working off the presidential checklist. An op-ed in "The Wall Street Journal," a big foreign policy speech Wednesday at the National Press Club that he'll deliver with the help of a teleprompter.

Going up with warmer ads.

(BEGIN VIDEO CLIP FROM CAMPAIGN AD)

UNIDENTIFIED MALE: My father will make an incredible president.

(END VIDEO CLIP)

LLAMAS: All to show the Republican Party he's ready to step up.

Then this, in Florida, at the RNC spring conference, Trump's top adviser, Paul Manafort, caught on tape telling a private meeting of top Republicans that underneath the rough and tumble primary persona, there's a more polished, more presidential reality.

PAUL MANAFORT, CAMPAIGN MANAGER, DONALD TRUMP: He gets it. The part he's been playing is (INAUDIBLE) is a part that now you've been expecting.

LLAMAS: And just like that, the primary now a fight over the truth about Trump,

SEN. TED CRUZ (R-TX), PRESIDENTIAL CANDIDATE: Donald Trump is a master illusionist. He is the Harry Houdini, engaged in an act of misdirection. Trump is a phony.

LLAMAS: Trump fired back, attacking Cruz.

TRUMP: He walks in bible held high. Then he puts the bible down and then he lies. He's a liar.

LLAMAS: Telling another crowd, if he wasn't who he was, he wouldn't be ahead and they wouldn't be there.

TRUMP: If I acted presidential, I guarantee you that this morning, I wouldn't be here. I'd have a -- an audience of about three people here in the front instead of this is the biggest crowd in the history of this school.

LLAMAS: As the primaries grow fewer and the convention draws nearer, some Republicans still waiting for the real Donald Trump.

For THIS WEEK, Tom Llamas, ABC News, New York.

(END VIDEOTAPE)

STEPHANOPOULOS: And GOP Chair Reince Priebus joins us right now.

Mr. Chairman, thanks for joining us this morning.

You were at that meeting down in Florida where Trump's campaign manager, Paul Manafort, spoke.

So which is the real Donald Trump and how did it play?

REINCE PRIEBUS, CHAIRMAN, REPUBLICAN NATIONAL COMMITTEE: Well, look, I -- I think there's a little bit of truth at every -- at every angle here. I think you're seeing Donald Trump at these rallies and I think what he's trying to say at these rallies is that if he was just politically correct, people wouldn't be there. And I also think that Paul Manafort and people like Rick Wiley understand that being presidential and being at 30,000 feet is something that's going to be really important in the home stretch.

So, yes, we think that tone matters and -- and being presidential, it does matter. And I get the sense that they get that.

But we'll wait and see.

STEPHANOPOULOS: Meanwhile, it's gotten the attention of Hillary Clinton. And her campaign coming out with this new ad.

(BEGIN VIDEO CLIP FROM CAMPAIGN AD)

TRUMP: They're bringing drugs, they're bringing crime, they're rapists, a total and complete shutdown of Muslims entering the United States.

PRIEBUS: Well, look, I mean and -- and we're starting the general election campaign, too. We had two soldiers from Benghazi at the RNC meeting who were lied to by Hillary Clinton, who did an awful job as secretary of State.

So, look, I mean there's going to be plenty of return fire, I can assure you of that.

But right now, as you know, we're in the middle of trying to figure out who our nominee is going to be. I feel good about where we're at as a party and the fundamentals on border registration, on -- on work in the field, on data, on being a party ready for a general to keep the House and the Senate.

But, look, we're -- we're working hard to make sure that we've got an open and fair convention so that we get to that place where we can unify around one person.

STEPHANOPOULOS: You say you feel good about that, but you've got a lot of prominent supporters in the Republican Party still holding out, including Charles Koch. In this exclusive interview with Jon Karl, he says -- he said he'd probably be sitting out the general election.

And then he goes on to say this.

(BEGIN VIDEO CLIP)

KARL: So is it possible another Clinton could be better than another Republican this time around?

KOCH: It's possible. It's possible.

KARL: You couldn't see yourself supporting Hillary Clinton, could you?

KOCH: Well, I -- that -- her -- we would have to believe her actions will be quite different than her rhetoric, let me put it that way.

(END VIDEO CLIP)

STEPHANOPOULOS: Mr. Chairman, it's pretty remarkable that someone who's done so much for your party would go that far, saying he's considering Hillary Clinton. And he's not alone.

Is the party really unifying behind -- behind Donald Trump or Ted Cruz right now?

PRIEBUS: Well, I mean it's pretty split. I mean obviously, you can see it out there. I mean it's a -- it looks like a, you know, on the delegate front, obviously Trump's got a little bit of a lead. But you look on the delegate selection front, it looks like a pretty split decision.

So I think it's going to be a close contest going into the next 60 days.

But look, Charles Koch -- and I know David and Charles, and Charles in particular has oftentimes gone out of his way to appear non-partisan. And maybe he is. I don't know.

But, you know, certainly they have their own activities that they work on. We have ours. There isn't actually that much intersection between the two.

We're prepared to win in November...

STEPHANOPOULOS: Well, they've funded Republican candidates...

PRIEBUS: -- but we're also prepared to...

STEPHANOPOULOS: -- all -- all down the ballot.

PRIEBUS: Well, sure they have.

STEPHANOPOULOS: All across the country.

PRIEBUS: But, yes, they have. But you have to admit that Charles, in the past, has gone out of his way to make the case for him being a little bit less partisan than people would -- would expect. I mean that's all I'm saying.

But -- but look, the -- the point here is that eventually, we're going to -- everyone is going to run out of time to analyze this. And we're going to have a nominee. And it's going to come down to four to eight more years of Barack Obama and Hillary Clinton or a different direction.

And I think that's going to be a very powerful case that we're going to be able to make as a party.

STEPHANOPOULOS: Meantime, Charles Koch is saying he's not going to go the convention. And he's not alone. Senator John McCain saying he probably won't go. Other Senate candidates, like Mark Kirk, Kelly Ayotte, saying they're not going to go at all.

Are you confident you're going to have your party behind you at this convention, given the tone of this campaign?

PRIEBUS: I don't remember seeing some of those folks at the convention in the past. I mean I'm sure that Mark and Kelly...

STEPHANOPOULOS: Well, John McCain was your nominee.

PRIEBUS: -- and that the senator has. But I don't know if the -- I don't know -- I just -- that's what I just qualified. What I was saying is I don't remember seeing Charles Koch at any other convention, so I don't know whether that's news or not.

I mean, look, this is going to be potentially a pretty historic event. Some people gravitate toward that conflict. Other people run from that conflict. I mean, the point is it's going to be up to the individual. Some people like the idea of an open convention with a floor operation.

Some people don't enjoy that. So, look, it's going to be up to them. It may very well be historic. And the point is, though, eventually, we're going to have a nominee and we're going to have a very stark contrast between those two choices.

And given Hillary Clinton's record on being trustworthy and being honest and the fact that things aren't going that well under Barack Obama, I think that we're going to have a very strong case to make to the American people.

STEPHANOPOULOS: You also got a lot of conservatives now, they're still talking about the possibility of a third party draft if Donald Trump does indeed get the nomination, including getting behind someone like the former Marine general, James Mattis (ph).

Have you talked to party leaders about that, other conservatives about that and how concerned are you?

PRIEBUS: Yes, I've talked to lots of folks within the party and the conservative movement and they all conclude that it's a dumb idea and it's never going to work and it's not going to happen.

So if so, you know, they're already behind the 8 ball and in some states they might not be able to get on the ballot. So -- and by the time we get to Cleveland, it's definitely going to be too late.

And, again, I don't know anyone truly serious that has any money behind them and the organization to make it happen really thinking that it's going to happen. It's a nothing burger and it's something that the media likes to spin. But -- and I don’t buy it.

STEPHANOPOULOS: Looking ahead to the convention, Donald Trump said this week that he would want to change the Republican platform on abortion, include specific exemptions for rape, incest and life of the mother.

Are you open to that?

And how about open to other changes to accommodate parts of his platform, like building this wall on the southern border and banning the entry of Muslims into the United States?

PRIEBUS: Well, look, I mean, the platform is up to the delegates at the convention. So if that's what Donald Trump is intending, then he needs to make sure that the people that agree with him are the people that are getting elected to the platform committee.

I think our platform's pretty clear on those subjects. We believe that life begins at conception and that 14th Amendment rights apply to unborn children. And I would suspect that that's what the platform is going to say after Cleveland.

STEPHANOPOULOS: Last time you were on you said the chances of a contested convention in Cleveland were going up.

Are they going down now?

PRIEBUS: I think they've plateaued, George.

STEPHANOPOULOS: OK, Mr. Chairman, thanks for joining us this morning.

PRIEBUS: (Speaking foreign language).

STEPHANOPOULOS: (Speaking foreign language).

"Thank you" from my fellow Greek.

Let's go to the roundtable right now, joined by Jon Karl; Republican strategist Ana Navarro; Democratic Jennifer Granholm from the pro-Hillary group Correct the Record; and our dueling editors, Bill Kristol from "The Weekly Standard" and Katrina Vanden Heuvel from "The Nation"

And, Jon, let's begin with that idea that the contested convention may have plateaued; that's what Reince Priebus says. New polls out this morning show Donald Trump ahead in Pennsylvania, ahead in most of Tuesday's states, even ahead in Indiana next week.

If he continues to run the table, there may not be a contested convention.

KARL: No question about it. If he pulls -- if he stays in this current trajectory, he will get to 1,237 before the convention. He will clinch it in time.

And, look, Cruz knows this. That's why you see Cruz going over the top. And as a response to this transgender bathroom issue. And I wouldn’t be surprised to see him do something like throw a real Hail Mary here, like appoint, name a running mate before Indiana.

STEPHANOPOULOS: Even before Indiana?

KARL: I could see him wanting to get out there --

(CROSSTALK)

KARL: -- to get out there and to -- and to have a running mate basically for the primaries, for the rest of the primaries.

STEPHANOPOULOS: And, Ana Navarro, he's going right at Ted Cruz is going right at this idea of a Trump makeover.

ANA NAVARRO, REPUBLICAN STRATEGIST: He is. And it does feel like a Trump makeover right now. I look at what he's done this week and I think to myself, oh, my god, I need to lay down. I actually agree with him with this stuff he has said.

Certainly of the transgender bathroom, where he has come out with a moderate position, talking about changing the platform so that it includes some expectations on abortion.

I mean, so, if he's appealing to me, he can't be appealing to a lot of the people that have -- he has been appealing to for the last --

(CROSSTALK)

STEPHANOPOULOS: -- can that play --

NAVARRO: -- (INAUDIBLE).

BILL KRISTOL, "THE WEEKLY STANDARD": It's not appealing to me, either. And it's an easier, you know, sell --

NAVARRO: Oh, nothing appeals to you at this point.

(LAUGHTER)

KRISTOL: The only thing that appeals to me is what Reince Priebus attacks as a dumb idea, which is giving the American people a better choice than Hillary Clinton and Donald Trump, if Trump is the Republican nominee, which I agree looks increasingly like not a done deal. I think an independent candidacy is totally doable. I think it will happen. The ballot access problems are not. In the Super Bowl there are two --

STEPHANOPOULOS: -- coming up on the filing deadlines --

KRISTOL: -- oh, Texas, North Carolina. Every other state -- no other state's filing deadlines' before June 27th. You couldn't wait until the convention. You'd have to decide after Indiana, possibly after California. I think there will be legal challenges in Texas and North Carolina that the deadlines are too early.

In the '80s, five states were successfully challenged in federal court for having such early filing deadlines. And I think a lot of patriotic Americans are going to look at this choice and -- ranging from activists to donors to possible candidates and say the country deserves better than a Clinton-Trump choice.

STEPHANOPOULOS: And meanwhile, Katrina Vanden Heuvel, I was struck by this sensation that Paul Manafort made when he went to the RNC this week.

He says personality problems which Trump may have are fixable but character problems, which Hillary Clinton has, are not.

KATRINA VANDEN HEUVEL, "THE NATION": You know, we're looking at the shameless reinvention of Donald Trump and what strikes me is that unless we've become the U.S. of Amnesia, people are going to remember he's insulted women, what he's demagogued about Muslims and immigrants.

Again, you know, I come back to a point I've made on this program. Media malpractice is going to be very important for the media to hold, if Donald Trump is the nominee, to hold him to account for what he has said. Obviously, whoever is the Democratic nominee will.

But I think we can't forget that. I thought the Koch interview, by the way, was really interesting because you saw the Koch brothers very angry about what happened, that they can't control a party.

And the Tea Party, which they ceded essentially, doesn’t hate Donald Trump that much. I mean, they're working with him. So --

NAVARRO: (INAUDIBLE). I think he (INAUDIBLE), which is I think --

(CROSSTALK)

VANDEN HEUVEL: He looks like a corporate leader who's kind of --

(CROSSTALK)

VANDEN HEUVEL: -- and who can blame him.

I mean, Bill, I feel like you haven't moved beyond the denial stage of grief yet. But --

(CROSSTALK)

KRISTOL: I'm sticking with denial.

VANDEN HEUVEL: I understand that. I understand --

KRISTOL: -- (INAUDIBLE).

VANDEN HEUVEL: As that was shown earlier, you know, this notion of him being able to Etch-A-Sketch his way to a new position, all those people who come to those rallies, not want a politician who has stood up before them and said, I'm authentic; I tell it like it is and, all of a sudden, flips to be something else on the one hand. And then on the other hand, for Democrats, you know, for -- or for the rest of the world, who are maybe moderate Republicans or establishment Republicans, you can't tell me that you're going to be persuaded that there's this whole new Donald Trump --

(CROSSTALK)

VANDEN HEUVEL: -- started to lean in that direction --

(CROSSTALK)

NAVARRO: I know who has successfully reinvented after the age of 50 is Madonna, OK?

(LAUGHTER)

NAVARRO: That being said Donald Trump gets judged by a completely different (INAUDIBLE) than practically any other politician.

KARL: And, you know, Trump has signaled at least a half a dozen times over the course of this campaign that he's going to transform -- this is somebody who can take three different positions in the course of a single sentence. So I'm not sure it's going to hurt him --

STEPHANOPOULOS: Here's the different coming up in a general election. This goes to your point, Katrina, you say -- I mean, part of the reason -- I mean, Donald Trump was asked and has been asked all these questions. But he was facing opponents who did not bring up a lot of these issues.

One of the things we've seen from that Hillary Clinton ad out already --

VANDEN HEUVEL: -- brought up. They will be brought up in a general campaign, which is going to be nasty, negative and vicious.

But I wouldn’t exclude --

KARL: But not short.

VANDEN HEUVEL: -- Ted Cruz -- not short -- because I think one of the problems we have in personalizing the racism and the hatred, that bullying that Donald Trump has brought to the Republican Party is is Ted Cruz, and the party, has -- they have become purveyors of a political culture that is changing, the Demographics of this country are changing. They are out of sync, which is what (inaudible) is so true, this is -- Etch-a-Sketch seems real retro. We're now into Extreme Makeover, reinvention. How far it goes, again, will be not only up to the Democratic candidate, but it must be up to a media to hold this candidate accountable.

And on the independent front, may I just say, I think the Republican Party is in trouble when it seeks salvation in a general.

KRISTOL: Well, let's take -- Jim Mattis happens to be a social liberal. He's more liberal than I am. He's very concerned about the debt. He's a strong national security hawk. Why wouldn't someone like him...

VANDEN HEUVEL: Because he hasn't been participating in the whole election. You will have -- there will be a riot in Cleveland...

KRISTOL: The facts. The facts. I'm saying if Trump was the Republican nominee, the laws permit independent candidates to petition to get on the ballot. It has happened. Ross Perot got 19 million votes. Jim -- or John Kelly, or many other people.

STEPHANOPOULOS: Setting aside denial, though, this gets to the question of is the base of the party, though, going to come behind Donald Trump if he gets the nomination? There will be some who will not. But Ana Navarro, do you think that you're going to get the kind of unity that Reince Priebus said he was starting to see in Florida this week?

NAVARRO: I think it's going to be a huge challenge for whomever the nominee ends up being. And right now, you know, they're all trying to reinvent themselves. You know, Ted Cruz is trying to be more likable. Donald Trump is trying to be more presidential. John Kasich is trying to be relevant.

And, you know, any of them may win the nomination. And I don't think we're going to get an Archangel Michael that shows up in the middle of the thing like an apparition and saves -- any of them is going to have a very big challenge. Because there is a split right now in the Republican Party. And it is...

KRISTOL: Answer this question, George, the most recent Republican nominees: Mitt Romney, John McCain, George W. Bush, will any of them support Donald Trump for president? I'm not so sure they will. Would they prefer to support even someone like a retired General Mattis or Kelly or other possible candidate.

(CROSSTALK)

VANDEN HEUVEL: I would like to ally with Bill Kristol on one thing. I do think we need a pro-democracy movement in this country to ensure that there is ballot access. We don't -- at the moment we don't have -- we're a poor country. We have two political parties. We don't (inaudible).

STEPHANOPOULOS: We're going to take a quick break. We're going to talk about the Democrat's endgame. What's Bernie Sanders's next move after that big loss in New York. He's live next.

Plus, Virginia's governor restores voting rights to felons who paid their dues, an historic move on civil rights or political favor to Hillary Clinton? Terry McAuliffe defense his decision in an ABC News exclusive.

And that other exclusive, Charles Koch breaking his silence in the 2016 race lashing out at Donald Trump's big ideas.

(BEGIN VIDEO CLIP)

KOCH: I mean, this isn't Nazi Germany. I mean, that's monstrous as I said at the time. So, obviously we totally oppose that.

Well, you know what, if we buy that, shame on us. He's already said what he wants to do. And he wants to go after every one of the rights we have.

(END VIDEO CLIP)

STEPHANOPOULOS: Hillary Clinton in Rhode Island last night, looking ahead to the general election and Donald Trump. But Bernie Sanders is doubling down, vowing to fight on through June. And he joins us live after this report from ABC's Cecilia Vega.

(BEGIN VIDEOTAPE)

CECILIA VEGA, ABC NEWS CORRESPONDENT: A double digit loss in New York and another tough night looming Tuesday. Bernie Sanders is now so far behind in the delegate count, it's hard to see a path out.

But the Vermont Senator is still vowing to stay in it...

SANDERS: We need a political revolution, millions of people standing up and fighting back.

VEGA: But could a protracted debate hurt the party and the eventual nominee?

The latest attack coming from Donald Trump.

TRUMP: So, Bernie Sanders, not me, said she's not qualified. So now I'm going to say she's not qualified, OK.

VEGA: Clinton says history shows she could unite the party.

CLINTON: President Obama and I ran a really tough race for the entire primary season.

VEGA: Rewind to this month in 2008. Clinton locked in a fierce battle with Barack Obama.

BARACK OBAMA, PRESIDENT OF THE UNITED STATES: She's said I'm elitist, out of touch, condescending.

VEGA: But even amid that battle, an olive branch about Obama's electability.

STEPHANOPOULOS: The question is, do you think Senator Obama can do that? Can he win?

CLINTON: Yes. Yes. Yes.

VEGA: Today, it is Clinton who is winning, not just by delegates, but also by nearly 3 million more votes. Despite the long odds for Sanders, some of his supporters still refuse to be swayed.

You would not vote for Hillary Clinton?

UNIDENTIFIED FEMALE: I cannot bring myself to vote for Hillary Clinton. I do not believe in her.

UNIDENTIFIED FEMALE: People talking about voting for the lesser of two evils, I don't believe in the idea of that.

VEGA: The question for Sanders now, could a drawnout endgame hurt not just his rival, but also what he and his supporters stand for.

For This Week, Cecilia Vega, ABC News, New York.

(END VIDEOTAPE)

STEPHANOPOULOS: And let's talk to Senator Sanders about that right now. Senator Sanders, thank you for joining us again think morning.

We showed in that piece, Donald Trump is now mimicking your arguments about Hillary Clinton. Does that concern you?

SANDERS: Not at all. I mean, Donald Trump lives in his own world. He insults everybody for every reason. He'll attack me. He'll attack Hillary Clinton. He'll attack his own opponents, his own Republican opponents. That does not concern me.

What does concern me is that we need to continue this debate, George, about what is happening to ordinary people in America. And that is that the middle class continues to decline. I was in Baltimore yesterday. The level of poverty there is beyond belief. The fact that we have so much income and wealth inequality, the fact that so many of our kids are graduating college deeply in debt, the fact that we're really not engaging in the planetary crisis of climate change, these are the issues that we need to be debating.

And we're going to take our campaign through California, through the D.C. primary. We're winning a whole lot of support. I believe that after winning 16 states already, we're going to win a lot more throughout this process.

And I think, by the way, George, this is good for democracy, it's good for the Democratic Party.

STEPHANOPOULOS: Meantime, Hillary Clinton is 80 percent of the way there on the delegates she needs to get the nomination. She's ahead in the most recent polls in Pennsylvania, most of the states coming up on Tuesday. Also poll out just this morning showing she's ahead in Indiana as well.

And David Plouffe, who ran, of course, President Obama's campaign, says -- sent out a tweet saying you've running a stunningly strong campaign fueled by passioned supporters, but raising money and your fundraising by stating you have a path to the nomination is a fraud. Your response?

SANDERS: Well, you know, David Plouffe is working for the Clinton campaign. And when you talk about raising money and fraud, well you know what, we have raised $7 million individual campaign contributions, more than any candidate I believe in history, averaging $27. And we intend to take the fight all the way to California so people throughout this country have a right to determine who they want as president and what kind of agenda they want for the Democratic Party.

Secretary Clinton, helped by David Plouffe and others, have raised enormous amounts of money on Wall Street from special interests. So I would suggest Mr. Plouffe, don't start criticizing me, who have raised money from ordinary people in small amounts, is doing something fraudulent.

I think the people of California, I think the people in 10 remaining states, do have the right to vigorously participate in the political class. And I think when people participate, voter turnout goes up. And when voter turnout goes up, Democrats win and Republicans lose.

STEPHANOPOULOS: If the contest doesn't go the way you hope, will you be able to follow the Clinton model of 2008, which she talked about on this "GMA" town hall this week, and make an enthusiastic case for her, the way she pushed for President Obama?

SANDERS: Well, that is totally dependent on what the Clinton platform is and how she responds to the needs of millions of Americans who are sick and tired of establishment politics and establishment economics.

You know, I can't snap my finger and tell people what to do. But what I will do is do everything that I can to make sure that somebody like a Donald Trump or some other right-wing Republican, does not become president of the United States. We do not need more tax breaks for billionaires, more cuts to Social Security, Medicare, more ignoring the facts.

Republicans don't even accept the reality of climate change, let alone being prepared to do something about it.

So I will do everything that I can to defeat any Republican candidate. If Secretary Clinton is the nominee, she is going to have to make the case to the American people, not just to my supporters, but all Americans, that she is prepared to stand up to the billionaire class, she is prepared to fight for health care for all Americans, that she is prepared to pass paid family and medical leave, make sure that college is affordable for the young people in this country.

That is what she has got to do. And I hope, if she is the nominee, that she does that well.

STEPHANOPOULOS: Would it help if she picked a vice presidential candidate from your wing of the party?

SANDERS: Look, I think that the American people are very tired of establishment politics and establishment economics. I think they're tired of a Congress that gives tax breaks to people who don't need them, but ignore the fact that we have 47 million people living in poverty.

So I think that if Secretary Clinton is the nominee -- and we're not giving this thing up, we're going all the way to California. But if she is the nominee, I would hope that she puts together the strongest progressive agenda that says, yes, we're going to stand with the working families in this country. We are prepared to take on the fossil fuel industry and the drug companies Wall Street and the billionaire class.

And if she has a candidate for vice president who is prepared to carry that mantle, prepared to engage in that fight, I think that would be a very good thing for her campaign.

STEPHANOPOULOS: You know, you seem to have an unlikely ally now in Charles Koch. In that interview with Jon Karl, he seemed to agree that the economic system is, in many ways, rigged.
listen.

(BEGIN VIDEO CLIP)

KARL: You -- you agree that this system is rigged?

KOCH: Absolutely.

KARL: -- is rigged in favor of -- of the wealthy?

KOCH: Because this two-tiered society creates welfare for the wealthy and -- and creates obstacles to opportunities for the disadvantaged.

(END VIDEO CLIP)

STEPHANOPOULOS: Do you think there's a way to keep your movement alive in a bipartisan way going forward?

(AUDIO GAP)

STEPHANOPOULOS: Sorry, Senator.

Do you -- do you think there's a way to keep your movement alive in a bipartisan way going forward?

SANDERS: In a bipartisan way going forward?

Well, you know, I think when you talk to the Koch brothers, understand what they mean, George. These guys want to eliminate Social Security. They want to eliminate Medicare and Medicaid. They want to basically do away with virtually every major piece of legislation that has been passed since Franklin Delano Roosevelt was president.

That is their understanding of what government should be about. And needless to say, that is not my view.

On the other hand, I think you've got a lot of Republicans out there, working class Republicans, who understand that there's something wrong when their kids can't afford to go to college, something wrong when their jobs have gone to China and Mexico and they're making 50 percent of what they used to make.

We have, in Vermont -- and I think in this campaign -- attracted a number of working class Republicans who understand that it's important to have a government that fights for all of us and not just the 1 percent.

But why, that is not what the Koch brothers believe. They believe quite the -- quite the contrary.

STEPHANOPOULOS: Senator Sanders, thanks very much for joining us this morning.

SANDERS: Thank you.

STEPHANOPOULOS: And when we come back, Virginia governor, Terry McAuliffe, drawing fire for his landmark decision to restore voting rights to convicted felons, even the most violent.

Plus, more of Jon Karl's exclusive interview with Charles Koch.

(BEGIN VIDEO CLIP)

KARL: But I'm sure you've been asked to contribute to the "Never Trump" movement.

KOCH: We have.

KARL: And why not get involved in that?

I mean here's a guy that...

KOCH: Because that's not what we do.

(END VIDEO TAPE)

(COMMERCIAL BREAK)

STEPHANOPOULOS: President Obama overseas this week on one of his final foreign trips, but of all his meetings, it's his chat with Prince George that's getting the most buzz.

(BEGIN VIDEO CLIP)

OBAMA: I guess you all know why I came this week. it's no secret. Nothing was going to stop me from wishing Happy Birthday to Her Majesty and meeting George, who was adorable.

(END VIDEO CLIP)

(COMMERCIAL BREAK)

STEPHANOPOULOS: Virginia governor Terry McAuliffe invoked his state's racist past when he restored the right to vote to convicted felons who served their sentences. It caught supporters and critics by surprise. And we're going to speak live to the governor after this report from Pierre Thomas.

(BEGIN VIDEOTAPE)

GOV. TERRY MCAULIFFE (D), VIRGINA: We will ensure that every Virginian with the freedom to live in our communities also has the right and the responsibility to participate in our democratic process.

But 200,000 votes is enough in theory to potentially swing the election of a swing state. And some Republicans say this is not about justice but sheer politics

Virginia delegate Chris Head telling CBS affiliate WDBJ…

CHRIS HEAD, VIRGINIA DELEGATE: It really is obvious to nobody who's paying attention that this is a direct desire to bring 200,000 new voters that will support Hillary Clinton. His whole governorship has been revolved around delivering Virginia to Hillary Clinton.

THOMAS (voice-over): A claim that has McAuliffe, a former chair of the Democratic National Committee and a big backer of Hillary Clinton, scoffing.

UNIDENTIFIED MALE: All of the evidence is suggested that it could be compromising public safety in part by pushing people farther out of mainstream American civic life.

THOMAS (voice-over): Almost 6 million people nationwide are barred from voting because of past felonies, according to the non-profit Sentencing Project. The number's pushing members of both parties to pursue criminal justice reform; 23 states have taken action to get some felons back on the voting rolls.

In Virginia, McAuliffe took it a step further than most, restoring voting rights to all ex-felons, even the most violent, potentially rapists and murderers. For THIS WEEK, Pierre Thomas, ABC News, Washington.

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STEPHANOPOULOS: And Governor McAuliffe joins us now.

Thank you for joining us this morning, Governor McAuliffe.

And let me begin with that point that Pierre ended with right there. You've been getting some heat for including even the most violent convicts in this order. Here's what delegate Robert Bell (ph) from the Virginia Assembly said.

He said, "Murder victims don't get to sit on juries but now the men that killed them will. A murder victim won't get to vote but the man that killed them will."

Your response?

MCAULIFFE: First of all, when I did this order, nobody should be surprised. This is something I campaigned on and I've been working for the restoration rights for the last two years as governor.

I have already restored the rights of 18,000 individuals, more than my past seven governors combined.

So the next natural step after meeting these folks and talking to them is everybody ought to have a second chance. Second chances matter. These folks, George, understand they have served their time; they're done with probation or parole. They're back in society. They're living in our communities. They have jobs. They're paying taxes.

Why don't we possibly want them to vote?

Why are we putting walls up?

So once you have paid your debt to society -- and that debt was determined by a judge and a jury -- once you have finished that, why should we have a lifetime ban?

And that's why I stood in front of our capital and erased 115 years. We have had some very horrible disenfranchisement of voters in Virginia. And I stood right in front of that capital, where we had a poll tax, literacy tax, disenfranchisement of voters. I stood not 20 yards from where Abraham Lincoln met the freed slaves 151 years ago in April.

It was the right thing to do legally and most importantly, George, it wasn't politics. It was the right thing to do morally. And I know these Republican legislators think it's politics.

We have elections every year in Virginia. And if I were to do this for political reasons, I would have done it last year, when I had my General Assembly up. And if I'd picked up 5,000 more votes, I'd have control of the state senate.

(CROSSTALK)

MCAULIFFE: -- won the last six elections statewide Democrats.

STEPHANOPOULOS: You say it's not politics but, boy, every headline in your state actually made this move -- we're going to show some of them right now -- did talk about this idea that it's an election year ploy to help Hillary Clinton. I know you scoff at that.

But this could make the difference in a close race, couldn't it?

MCAULIFFE: Well, I would tell the Republicans quit complaining and go out and earn these folks' right to vote for you. Go out and talk to them. I find it very -- and in fact, I think some of the language that has come out of the Republicans, I would tell them to be very careful at how they frame this, very careful of their rhetoric.

They have an opportunity to go out and get these individual new voters to vote for them. But make your argument. These are the same legislators, George, that, just in this session, sent me a bill to sign that would have been very similar to North Carolina, religious freedom bill, that would have rolled back the rights and given protections to those who didn't discriminate against LGBT members. They sent me a bill that would have defunded parts of Planned Parenthood. This is the same group of individuals several years ago passed the transvaginal ultrasound against women.

I told folks when I ran for governor, I will be a brick wall to protect your rights for women. I will protect the rights of LGBT members and I'll do everything I can to get disenfranchised voters entrenched.

So I've done that. It's exactly what I talked about. Our economy is booming. I just announced a 4 percent unemployment, biggest budget surplus in Virginia history. We put $1 billion in education. It works when you welcome people back into society and make them feel good about themselves.

STEPHANOPOULOS: And finally, Governor, even your Democratic predecessor, Tim Kaine, thought that this kind of a blanket order stretched the boundaries of executive clemency power.

Are you confident it's going to withstand a legal challenge?

MCAULIFFE: There is no question. Actually, the attorney general has reviewed this, as well as the scholars that we have had in Virginia have said it is the governor's sole authority to do clemency. It has nothing to do with the general assembly.

So I have the full authority to do this. I looked at this. I spent a lot of time looking at this issue, George. But I have legal authority, but I also have the moral authority.

Let's let people back in. Second chances matter. They've served their time. They're in our communities.

Why not let them vote?

I don't understand. I'm not giving you your gun rights back. I'm not reducing your sentence. I'm merely saying after you have served your time and your probation and your parole are all over, determined by a judge and jury, I want you feeling good about yourself. I want you voting.

STEPHANOPOULOS: Governor McAuliffe, thanks for joining us this morning.

MCAULIFFE: Thank you.

Thank you, George.

STEPHANOPOULOS: Our powerhouse roundtable coming up next.

Who's on their VP short list?

We're going to find out when we come back.

(COMMERCIAL BREAK)

STEPHANOPOULOS: Now to that THIS WEEK exclusive with Charles Koch. The powerful billionaire rarely speaks out in public, but he and his brother David have spent hundreds of millions to elect Republicans at all levels.

And Jon Karl traveled to Kansas, where Koch, who recently wrote the book, "Good Profit," explained why he probably won't back the GOP nominee.

(BEGIN VIDEOTAPE)

KOCH: Well, I'll tell you why. We said here are the issues. You've got to be like Ronald Reagan and compete on making the country better rather than tearing down your opponents.

And right off the bat, they didn't do it. More of these personal attacks and pitting one person against the other, that's the message you're sending the country. That's the way you should -- you're role models and you're terrible role models.

So how -- I don't know how we could support him.

KARL (voice-over): We traveled to Wichita, the headquarters of Koch Industries, where the 80-year-old CEO, Charles Koch, the ninth richest person in the world, according to "Forbes," works every day, paying with cash to eat in the company cafeteria and taking the stairs to his third floor office.

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UNIDENTIFIED MALE: The Koch brothers.

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KARL: To their critics, Charles and his brother David are the money manipulators, a powerful and secretive force driving an ultra-conservative agenda with their vast wealth and anonymous donor network.

UNIDENTIFIED FEMALE: Billions for big oil.

KARL: When you look back over the years, over the last several cycles, hundreds of millions of dollars in -- in electoral politics, but what have you gotten for that?

KOCH: Well, I've gotten a lot of abuse out of it.

KARL: Yes.
you've been called un-American.

KOCH: Yes.

KARL: On the Senate floor.

KOCH: Yes, well, I'm -- yes, I'm out there.

What have we gotten for it?

There have been some good things, particularly at the state and local level. But the national politics is -- has been disappointing...

KARL: Over the last six years, you -- you got government shutdowns, you got a Republican Party that is -- seems to be the center of gravity, is anti-immigration, critical of free trade.

People say you control the Republican Party because of all that money.

KOCH: Well, if I controlled the Republican Party, we would not have a two-tiered system. We would not have a tax code that subsidizes the wealthy. We would get rid of all of that.

So obviously, I don't control anything.

KARL: So many people in the country now look at the American economy and they say that it's rigged -- the rich get richer and it's, you know, a working class person has a hard time getting by. Wages are stagnant. They say it is rigged. It's rigged by those at the top.

KOCH: It is, and that's-- that’s in the policy area that's our number one policy objective to change that. What I call it is--

KARL: So you agree that the system is rigged?

KOCH: Absolutely.

KARL: Is rigged in favor of the wealthiest?

KOCH: In favor of companies like ours. Because we have this corporate welfare that benefits established companies and makes it very difficult for somebody to get started.

KARL: Well, and Republicans are adamant about protecting a lot of these tax breaks.

KOCH: Absolutely. No, and I can see why they say, 'Well, there's a tax break over here, we need one here.' Well that's the wrong attitude, we got to get rid of all of them. I don't hear any of the Republican candidates talking about this two-tiered system and getting rid of it. So that's why we haven't supported any of them.

KOCH: We read-- I read, oh, we've given millions to this one, millions to that one, and millions to oppose Trump. We've done none of that. We haven't put a penny in any of these campaigns, pro or con.

KARL: But I'm sure you've been asked to contribute to the Never Trump movement.

KOCH: We have.

KARL: And why not get involved in that? I mean here's a guy -

KOCH: Because that's not what we do. What we're trying to do is build alliances to make the country better. Like we have one with the White House on criminal justice reform. You do it by trying to find areas where you can work with everybody.

KARL: So are gonna sit out this presidential election?

KOCH: Well, we'll see. I mean, when we get a nominee then we'll explore that. And we don't want arm waving. We want to know specifics.

KARL: What did you think when you first heard Donald Trump’s proposal to put a temporary ban on all Muslims entering the United States?

KOCH: Well, obviously that's antithetical to our approach, but what was worse was this we'll have them all register. That's reminiscent of Nazi Germany. I mean that's monstrous as I said at the time.

KARL: And when you hear another top presidential candidate talking about making the sand glow and carpet bombing in the Middle East…

KOCH: Well, that's gotta be hyperbole, but I mean that a candidate, whether they believe it or not, would think that appeals to the American people. This is frightening.

KARL: When you look at the presidencies of George W. Bush and Barack Obama, which one in your view was worse? I know you don't like either one.

KOCH: I would compare it to, more toward Bill Clinton. Just in spending and regulation the government grew much more under Bush's administration, whose- I think is a fine person and tried to do the right thing but was misguided.

KARL: And got us involved in a war that you adamantly oppose.

KOCH: Yeah, and tried to create democracies in countries where that's counterproductive.

KARL: Am I hearing you correctly, you think Bill Clinton was a better president than George W. Bush?

KOCH: Well in some ways. In other ways, I mean he wasn't an exemplar. But as far as the growth of government, the increase in spending, on restrictive regulations, it was two and half times under Bush than it was under Clinton.

KARL: So is it possible another Clinton could be better than another Republican--

KOCH: It's possible.

KARL: Next time around?

KOCH: It's possible.

KARL: You couldn't see yourself supporting Hillary Clinton, could you?

KOCH: Well, I-- that-- her-- we would have to believe her actions would be quite different than her rhetoric. Let me put it that way. But on some of the Republican candidates we would-- before we could support them, we'd have to believe their actions will be quite different than the rhetoric we've heard so far.

(END VIDEOTAPE)

STEPHANOPOULOS: And you can see more of Jon's interview on ABCnews.com. And the Powerhouse Politics podcast, that's available on iTunes. We're going to be right back after this from or ABC stations.

UNIDENTIFIED MALE: I can't even fathom that. He said it's almost breathtaking.

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STEPHANOPOULOS: A lot of nos right there on veepstakes. Let's talk about who might be on the list right now starting with Jon Karl.

So, you got our attention earlier in the program. You said that Ted Cruz might pick someone to be his runningmate before the end of the primary on May 3. Any idea who?

KARL: But by the way, has anybody who actually was picked as a runningmate ever said before that they were interested?

I think what Cruz will do is he will double down on conservative. Usually with a runningmate pick, you're picking somebody to run in the general election. He will pick somebody who will help him in the rest of the primaries. This will be somebody who will be -- it's hard to get as conservative as Ted Cruz, but pretty much is conservative...

STEPHANOPOULOS: Meantime, Bill Kristol, Donald Trump has sort have been suggesting that he may reach out to someone from the establishment.

KRISTOL: Well, I think -- who knows how Donald Trump thinks about this. He certainly has reached out to the establishment hasn't he? Who is running his campaign now? Paul Manaford, the quintessential Washington insider, lobbyist, who has represented dictators all over the world.

I -- Kasich would be the obvious -- I do think it's perfect that Donald Trump, Mr. Outside, a time for a change -- I think Kasich would be an obvious pick for Trump if he wants to signal that he has some respect for governing experience. And Kasich would presumably the third.

STEPHANOPOULOS: Do you think there's any chance he'd take it?

NAVARRO: You know, I hope not. And I think there would go his entire career in Ohio, definitely. I'm not sure that he could help Trump. And I think that it would look -- on the Trump side, it would look like the ultimate deal, right, the art of the deal.

I think Trump needs to figure out how to make up the gap he has with either Hispanics, or women, or Hispanic women, i.e. Susana Martinez. I'm not sure she would take it...

STEPHANOPOULOS; Governor of New Mexico.

NAVARRO: I'm not sure if Nikki Haley would take it. I'm not sure if Susana Martinez, those two governors, would take it.

But over 70 percent of women have disapproval of him, over 80 percent of Hispanics.

KRISTOL: They're more likely to be vice presidential candidates for General Mattis or...

STEPHANOPOULOS: Let's talk about the Democratic side, meantime.

NAVARRO: You keep bringing up the Archangel Michael.

STEPHANOPOULOS: Katrina Vanden Heuvel, the Clinton team doesn't like all this talk about the VP pick right now, but John Podesta did open up the possibility saying a woman would be on the short-list. Of course, that has everybody thinking immediately of Elizabeth Warren.

VANDEN HEUVEL: Well, first of all, let me just say, you know, Bernie Sanders continues to run through the primaries. He goes to the convention. He fights for a progressive platform and procedural rule changes, gets rid of the super delegates. But nothing would unify the Bernie Sanders-Clinton wing more than Elizabeth Warren as a pick.

I do not think she will do it. I think she's most effective in the Senate. If she left the Senate, the Republican governor of Massachusetts would appoint a senator. Democrats need to take back the Senate, need five seats.

You know, there are other women on both sides. There's -- and I think, you know, it's no precedent to have a candidate pick people of the same gender, we've seen that. But, Sherrod Brown...

(LAUGHTER)

VANDEN HEUVEL: Sherrod Brown's problem is Ohio. We were talking, Jennifer and I, I mean, you want maybe a vice president who represents the diversity of this country, what we call the rising American majority.

STEPHANOPOULOS: Maybe Julian Castro.

VANDEN HEUVEL: But -- or Julian Castro. It would be great to have a woman, too.

STEPHANOPOULOS: Do you think, Jennifer, the calculation of the Clinton camp changes depending on if the nominee is Trump or Cruz?

GRANHOLM: I think they're the same, honestly. From the perspective on the Democratic side, they have the same types of policies. I do think that Katrina is right.

You know, I was here in New York for the victory night celebration for Hillary Clinton. It was amazing how much consensus and joy there was around this notion of unity and of a rising American majority, or a candidate that reflected all of America.

And so, you know, she doesn't -- she's focused on the primary. Bernie Sanders is still in. They don't...

STEPHANOPOULOS: You know (inaudible) a VP pick.

GRANHOLM: But -- well, I am certain that she would want somebody who is a fierce fighter for the things that she has been advocating for, for a lot of the things that Bernie Sanders talked about early...

KARL: What about a former governor from a place like Michigan. Somebody like a Jennifer Granholm.

(CROSSTALK)

(LAUGHTER)

(CROSSTALK)

GRANHOLM: I have a personal -- I -- in this list of people that are being considered, a law school confidante of ours, somebody who is a dear family friend who we vacation with all the time is Tom Perez. He is (inaudible) great guy...

(CROSSTALK)

NAVARRO: If she needs a Sanders on the ticket, she should look at Jane Sanders. I think the spouses in 2016 has been very impressive on both sides.

GRANHOLM: But as unifying as Elizabeth Warren would be, I think the platform fight is going to be very important at the Democratic Party.

STEPHANOPOULOS: Clearly, Sanders....

GRANHOLM: Because Sanders, you know, he went from 3 percent last year when he announced his candidacy to where he is today, because trying to reposition our politics, our democracy...

(CROSTALK)

NAVARRO: Between Sanders and Elizabeth Warren, because it seems to me he...

STEPHANOPOULOS: We're going to have to end on that question, because we are out of time.

(CROSSTALK)

STEPHANOPOULOS: Sorry guys. The computer is going to hit any second. Get some more on "GMA".